You definitely deserve to look and feel better! Looking rested and put together can be hard when you're a busy mama, but it's not totally impossible.
How can I make casual clothes look nice?
First and foremost, make sure your clothes fit well. Even jeans and a t-shirt can look pulled together as long as they fit your body properly (not too loose, not too tight). Of course, clean and unwrinkled clothes look better than items pulled off the bottom of a laundry basket. Find an accessory or two that you love to add some oomph to your outfit- a great necklace, pretty earrings, a beautiful scarf- and you'll feel much more glamorous than you would otherwise.
How can I wear makeup that makes me look pretty but doesnt feel gunky?
Try mineral makeup. MAC makes a mineral makeup powder that I swear by for daily use (I rarely wear foundation). There are lots of other companies that make mineral powder, blush, eyeshadow, etc. Try Googling "mineral makeup." or check out Etsy.com to find independent makeup purveyors. You Tube has tons of videos that can teach you how to apply makeup if you need tips in that department.
No matter what kind of makeup you decide to use, be sure to moisturize your face well before applying it. Unmoisturized skin tends to cause makeup to settle in pores and lines and leads to the gunky feeling you wish to avoid.
How else can I look better?
Exercise and eat well. Rest, and try to take some time for yourself as often as you can. Easier said than done, but it really does work. Sorry if that's not helpful... I have trouble doing these things regularly myself.
Also - suggestions for best hairstyles for fine hair are appreciated (any natural dye ideas?)
I have fine, straight hair, and I find that it looks best with blunt ends (as opposed to a shattered-type cut, which makes the ends look fragile and fly-away). I blow dry my hair and use a pomade to keep it smooth. Invest in a good haircut- a good cut is easier to style and looks better with less product (if it needs product at all). Try to establish a relationship with one stylist who can get to know you well- not just your hair, but your lifestyle, too. This is important because a stylist who knows you well will suggest styles/cuts you can manage and will feel comfortable wearing.
I don't have much experience with natural hair color other than the DIY henna kits. I don't know of any stylists where I live who work with all-natural hair color, so you might be on your own if you want chem-free color. Henna can cause hair breakage in some cases, so if you use it, be sure to follow the package instructions carefully.
Best of luck! Let me know if you have any questions!